Rotary kiln large gear heat treatment process optimization system and method

Abstract

The present invention belongs to the technical field of gear heat treatment, and discloses a rotary kiln large gear heat treatment process optimization system and method; the method comprises: performing normalizing forging twice on a preselected material to obtain a preselected material with refined grains, processing the preselected material with refined grains to obtain a gear, performing vacuum nitriding treatment on the naturally cooled gear to obtain a first gear; performing gradient quenching treatment on the first gear to obtain a second gear; performing carburizing treatment and isothermal tempering treatment on the second gear to obtain a third gear; presetting a scanning range, scanning step length and scanning speed, and collecting X-ray diffraction patterns, neutron diffraction data and eddy current signals on the surface of the third gear; the present invention can effectively eliminate stress, dynamically adjust process parameters such as tempering, so that the heat treatment process is in a precisely controllable state throughout the entire process, and comprehensively improve gear performance.

Description

Technical Field

[0001] The present invention relates to the technical field of gear heat treatment, and more particularly to a system and method for optimizing the heat treatment process of large gears in a rotary kiln. Background Art

[0002] In traditional gear heat treatment processes, gear deformation during the carburizing heat treatment process is difficult to effectively control, which directly affects the gear's precision, strength, noise, and life. Even if a grinding process is added after carburizing, deformation will still reduce the gear's accuracy level. Many factors affect carburizing heat treatment deformation, including metallurgical factors of the gear material, preliminary heat treatment, carburizing process, and quenching. In addition, traditional processes have relatively simple means of stress relief and lack a real-time detection and feedback mechanism to optimize process parameters. This makes it difficult to meet the modern industry's requirements for high precision and high performance of large gears.

[0003] Chinese patent application publication number CN116162782A discloses a heat treatment process for escapement wheels for mechanical watches: step 1, heating the gear to 750±10℃ and keeping it warm for 2-3 hours; then continuing to heat it to 930±10℃ and keeping it warm for 4-5 hours; step 2, cooling the gear to AC3-10℃ and keeping it warm for 4-5 hours; step 3, cooling the gear to AC1-10℃ and keeping it warm for 5-6 hours; step 4, quickly cooling the gear to BS-10℃ and keeping it warm for 1-2 hours; step 5, quickly heating the gear to AC1-10℃ and keeping it warm for 5-6 hours; step 6, air cooling the gear to 650±10℃ and keeping it warm for 4-5 hours; step 7, quickly cooling the gear to 400±10℃, then slowly cooling it to 200℃, and air cooling it to room temperature after it is taken out of the furnace. The invention heats up to 930±10℃ in stages and keeps the temperature high so that the austenite grains are completely equiaxed after the gear forging blank structure recrystallizes, completely cuts off the tissue inheritance, and basically eliminates the processing stress generated during the forging process.

[0004] Although the above methods can meet most scenarios, research and practical application of the above methods and existing technologies have revealed that the above methods and existing technologies have at least the following defects:

[0005] The stress elimination is not targeted enough and the elimination means are single; there is a lack of real-time detection feedback mechanism to optimize process parameters.

[0006] In view of this, the present invention proposes a rotary kiln large gear heat treatment process optimization system and method to solve the above problems. Summary of the Invention

[0007] In order to overcome the above-mentioned defects of the prior art and to achieve the above-mentioned purpose, the present invention provides the following technical solution: a method for optimizing the heat treatment process of large gears in a rotary kiln, comprising the following steps:

[0008] The preselected material is subjected to normalizing forging twice to obtain a preselected material with refined grains, the preselected material with refined grains is processed to obtain a gear, and the gear is subjected to vacuum nitriding treatment after natural cooling to obtain a first gear;

[0009] Performing gradient quenching treatment on the first gear to obtain a second gear;

[0010] Carburizing and austempering the second gear to obtain a third gear;

[0011] Preset the scanning range, scanning step length and scanning speed to collect X-ray diffraction patterns, neutron diffraction data and eddy current signals from the surface of the third gear;

[0012] Extract features from X-ray diffraction patterns, neutron diffraction data, and eddy current signals to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; and concatenate the X-ray diffraction features, neutron diffraction features, and eddy current features to obtain a feature vector.

[0013] The characteristic vector is used as the input of the parameter prediction model to obtain the tempering temperature and tempering time, and the third gear is isothermally tempered according to the obtained tempering temperature and tempering time to obtain the fourth gear;

[0014] Strengthening the fourth gear through a multi-energy field coupling stress relief process to obtain a fifth gear;

[0015] The tooth profile data of the fifth gear is collected, and the fifth gear is fine-machined using a deformation compensation cutting strategy to obtain a large gear for a rotary kiln.

[0016] Furthermore, the method for obtaining the third gear includes:

[0017] The second gear is placed in a carburizing furnace, heated to 920-940°C at a rate of 10-15°C / min, and then carburized for 4-6 hours. During the carburizing process, the carbon content in the carburizing furnace is 1.0%-1.2%. After the carburizing is completed, the carburizing furnace is opened and the second gear is transferred to an isothermal quenching furnace at 280-350°C within 8-10 seconds for an isothermal salt bath, and kept warm for 2 hours. After the insulation is completed, the second gear is taken out and naturally cooled to room temperature to obtain the third gear.

[0018] Furthermore, the method of obtaining X-ray diffraction characteristics includes:

[0019] The position of each diffraction peak, the intensity value corresponding to the highest point of each diffraction peak, and the half-height width of each diffraction peak, that is, the width of the diffraction peak corresponding to half of the intensity value corresponding to the highest point of the diffraction peak, are extracted from the X-ray diffraction pattern; the position of the diffraction peak corresponds to the diffraction angle of Position, calculate the intensity ratio of adjacent diffraction peaks to obtain the peak intensity ratio; calculate the grain size of the third gear using the Scherrer formula; calculate the residual stress corresponding to different azimuth angles; and splice the peak intensity ratio, grain size, and residual stress as the X-ray diffraction feature.

[0020] Furthermore, the method for obtaining the neutron diffraction characteristics includes:

[0021] Extract the diffraction peak shift of the preset crystal plane at different depths from the neutron diffraction data and calculate the lattice strain; calculate the internal stress according to Hooke's law; and combine the lattice strain and internal stress as the neutron diffraction feature;

[0022] Methods for obtaining eddy current characteristics include:

[0023] The current in the eddy current signal and the current corresponding to the eddy current signal with changed phase and amplitude are obtained to calculate the crack depth; the crack size is calculated; and the crack depth and crack size are spliced together as the eddy current feature.

[0024] Furthermore, the method for obtaining the fourth gear includes:

[0025] The third gear was placed in a heating furnace, and the temperature of the heating furnace was raised to the tempering temperature at a heating rate of 5-10°C / min, and then kept at the tempering temperature for the corresponding tempering time. The third gear was taken out of the heating furnace and naturally cooled to room temperature in air to obtain the fourth gear.

[0026] Furthermore, the method for obtaining the second gear includes:

[0027] The first gear is placed in a quenching furnace, the temperature of the quenching furnace is raised to 860°C at a rate of 10-15°C / min, and then kept warm for 1.5-2 hours. After the insulation is completed, the first gear is transferred to a quenching tank filled with polymer quenching liquid within 5-10 seconds; the circulation pump flow rate of the quenching tank filled with polymer quenching liquid is adjusted to 600-800L / min, and the flow rate of the polymer quenching liquid is adjusted so that the cooling rate of the first gear is 80-100°C / s; until the temperature of the first gear drops to 495-550°C, the first gear is transferred to a quenching tank filled with water-based coolant within 3-5 seconds; the circulation pump flow rate of the quenching tank filled with water-based coolant is adjusted to 300-500L / min, and the flow rate of the water-based coolant is adjusted so that the cooling rate of the first gear is 30-50°C / s, until the temperature of the first gear drops to 190-210°C, to obtain a second gear.

[0028] Furthermore, the method for obtaining the fifth gear includes:

[0029] Step 1: Demagnetize the fourth gear for 5 minutes using a pulsed electromagnetic field with a frequency of 1 kHz and a magnetic field strength of 1.5 T;

[0030] Step 2: Use high-frequency ultrasound with a frequency of 20 kHz and an amplitude of 80 μm to impact the root fillet of the fourth gear for 10 minutes, setting the impact energy density to 15 J / cm²; simultaneously apply an alternating toroidal magnetic field with a frequency of 50 Hz and a magnetic field strength of 0.8 T;

[0031] Step 3: Use Nd:YAG laser with a wavelength of 1064nm and an energy density of 10J / cm² to perform impact treatment on the fourth gear for 5 minutes to obtain the fifth gear.

[0032] Furthermore, the method for obtaining a large gear for a rotary kiln includes:

[0033] A laser scanning probe is used to measure the tooth profile of the fifth gear. The probe scans along the tooth profile of the fifth gear to obtain the tooth profile data of the fifth gear. The tooth profile data of the fifth gear is compared with the pre-designed tooth profile data, and the tooth profile error data is calculated. The fifth gear is fine-machined according to the tooth profile error data based on the plasma-assisted cutting method. During the fine-machining process, the tooth profile of the fifth gear being machined is scanned and measured once at every preset time interval by the laser scanning probe. The measured tooth profile data of the fifth gear is compared with the pre-designed tooth profile data, and the tooth profile error compensation data is calculated.

[0034] Furthermore, the method for fine-machining the fifth gear according to the tooth profile error data based on the plasma-assisted cutting method includes:

[0035] Ar and H2 are mixed in a ratio of 5:1-10:1 to obtain a mixed gas, the mixed gas is introduced into a plasma generator, the plasma generator ionizes the mixed gas to generate plasma, the plasma generator is adjusted so that the temperature of the plasma is 110-130° C., and the plasma is injected into the cutting area at an injection pressure of 0.12 MPa; and a cutting tool is controlled to cut the fifth gear according to a preset cutting speed, a preset feed rate, a preset cutting depth, a preset rake angle, a preset clearance angle, and a preset edge radius to perform cutting processing according to the tooth profile error data;

[0036] Methods for obtaining tooth profile error compensation data include:

[0037] The heat treatment process parameters and machining process parameters are used as inputs of the deformation compensation model to obtain tooth profile error data. The difference between the tooth profile error data and the actually measured tooth profile error data is calculated, and the difference is used as the tooth profile error compensation data. The tooth profile of the fifth gear is compensated according to the tooth profile error compensation data. The heat treatment process parameters include the heating rate, furnace temperature and holding time during the gear heat treatment process. The machining process parameters include the plasma mixing ratio, temperature, injection pressure, cutting speed, feed rate, cutting depth, as well as the rake angle, clearance angle and edge radius of the cutting tool.

[0038] Furthermore, the method of obtaining the grain-refined preselected material comprises:

[0039] The preselected material is placed in a heating furnace, the temperature of the heating furnace is increased to 890°C at a heating rate of 5-10°C / min, and then kept warm for 4 hours. The preselected material is taken out of the heating furnace and naturally cooled to room temperature in the air; the preselected material is placed in a heating furnace again, the temperature of the heating furnace is increased to 850°C at a heating rate of 5-10°C / min, and then kept warm for 3 hours. The preselected material is taken out of the heating furnace and naturally cooled to room temperature in the air to obtain a preselected material with refined grains.

[0040] Furthermore, the method for obtaining the first gear includes:

[0041] After natural cooling, the gear is placed in a vacuum furnace with a pressure of 10-100Pa, and nitrogen is introduced into the vacuum furnace until the pressure inside the vacuum furnace is 500-1000Pa. The temperature of the heating furnace is raised to 520℃ at a heating rate of 5-10℃ / min and then kept warm for 8h. After the insulation is completed, wait for the temperature of the heating furnace to drop to room temperature, turn off the nitrogen, and take out the gear in the heating furnace to obtain the first gear.

[0042] A rotary kiln large gear heat treatment process optimization system implements the rotary kiln large gear heat treatment process optimization method, including:

[0043] Material pretreatment module: performing normalizing forging twice on the preselected material to obtain a preselected material with refined grains, processing the preselected material with refined grains to obtain a gear, placing the gear in air for natural cooling, and performing vacuum nitriding treatment on the naturally cooled gear to obtain a first gear;

[0044] Heat treatment module: performing gradient quenching treatment on the first gear to obtain the second gear; performing carburizing treatment and isothermal quenching treatment on the second gear to obtain the third gear;

[0045] Detection optimization module: Preset the scanning range, scanning step size, and scanning speed to collect X-ray diffraction patterns, neutron diffraction data, and eddy current signals from the surface of the third gear; perform feature extraction on the X-ray diffraction patterns, neutron diffraction data, and eddy current signals to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; concatenate the X-ray diffraction features, neutron diffraction features, and eddy current features to obtain a feature vector; use the feature vector as input to a parameter prediction model to obtain a tempering temperature and tempering time, and perform isothermal tempering on the third gear based on the obtained tempering temperature and tempering time to obtain a fourth gear;

[0046] Post-processing module: Strengthen the fourth gear through a multi-energy field coupling stress relief process to obtain the fifth gear;

[0047] Finishing module: collects the tooth profile data of the fifth gear, and performs finish machining on the fifth gear through deformation compensation cutting strategy to obtain the large gear of the rotary kiln.

[0048] The technical effects and advantages of the rotary kiln large gear heat treatment process optimization system and method of the present invention are as follows:

[0049] The present invention significantly improves the performance of large gears of rotary kilns through the synergistic effect of multiple working steps; refines the gear grains and strengthens the gear material foundation through two normalizing forgings; improves the wear resistance and toughness of the gears through vacuum nitriding, gradient quenching and carburizing treatments; accurately controls the tempering parameters based on multimodal detection data to effectively eliminate stress; constructs a real-time detection feedback mechanism through multi-source data collection such as X-ray diffraction patterns, and dynamically adjusts process parameters such as tempering to keep the entire process in a precisely controllable state, thereby improving gear performance in all aspects; and further improves dimensional accuracy and fatigue life through multi-energy field coupling stress elimination and deformation compensation finishing, meeting the complex working conditions of the rotary kiln. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic flow chart of a method for optimizing the heat treatment process of large gears in a rotary kiln according to the present invention;

[0051] Figure 2 is the X-ray diffraction pattern of the third gear of the present invention;

[0052] Figure 3 This is a flow chart of a method for obtaining a fifth gear according to the present invention;

[0053] Figure 4 This is a block diagram of the rotary kiln large gear heat treatment process optimization system of the present invention;

[0054] Figure 5 This is a schematic diagram of the interface of the rotary kiln large gear heat treatment process optimization system of the present invention. DETAILED DESCRIPTION

[0055] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0056] Example 1

[0057] See also Figure 1 As shown, the method for optimizing the heat treatment process of large gears in a rotary kiln according to this embodiment includes the following steps:

[0058] The preselected material undergoes two normalizing forgings to obtain a refined grained preselected material. This refined grained preselected material is then processed to produce a gear. After natural cooling, the gear undergoes vacuum nitriding to produce the first gear. The relatively slow natural cooling process of the gear allows for a uniform transformation of the internal structure and avoids thermal stress caused by rapid cooling. During the cooling process, the atoms within the preselected material have ample time to rearrange, further eliminating residual stress from previous machining and heat treatment, resulting in a more uniform stress distribution within the gear.

[0059] Methods for obtaining preselected materials with refined grains include:

[0060] The preselected material is placed in a heating furnace, heated to 890°C at a rate of 5-10°C / min, held at this temperature for 4 hours, removed from the furnace, and naturally cooled to room temperature in air. The preselected material is then placed in a heating furnace again, heated to 850°C at a rate of 5-10°C / min, held at this temperature for 3 hours, removed from the furnace, and naturally cooled to room temperature in air, resulting in a grain-refined preselected material. During the two normalizing forgings of the preselected material, the metal undergoes plastic deformation, eliminating residual stresses formed within the original preselected material due to casting and other factors. The rapid heating and cooling during normalizing forging recrystallizes the internal structure of the preselected material, further eliminating stresses generated by forging, refining the grains, and laying a good structural foundation for subsequent processing, reducing the possibility of new stresses being generated during subsequent processing.

[0061] Methods for obtaining the first gear include:

[0062] After natural cooling, the gear is placed in a vacuum furnace with a pressure of 10-100Pa. Nitrogen is introduced into the vacuum furnace until the pressure inside the vacuum furnace reaches 500-1000Pa. The furnace temperature is raised to 520℃ at a heating rate of 5-10℃ / min and then kept warm for 8 hours. After the insulation is completed, the furnace temperature is allowed to drop to room temperature. The nitrogen is then turned off and the gear in the heating furnace is removed to obtain the first gear. The vacuum environment reduces adverse factors such as oxidation. During the nitriding process, nitrogen atoms diffuse into the gear surface to form a nitride layer, which generates compressive stress on the gear surface. This offsets some of the internal tensile stress to a certain extent, thereby improving the gear's fatigue strength and stress corrosion resistance. Nitriding the gear tooth surface can also form a high-hardness diffusion layer on the gear surface, providing a base for subsequent laser composite strengthening.

[0063] Performing gradient quenching treatment on the first gear to obtain a second gear;

[0064] Methods for obtaining the second gear include:

[0065] The first gear is placed in a quenching furnace, the temperature of the quenching furnace is raised to 860°C at a rate of 10-15°C / min, and then kept warm for 1.5-2 hours. After the insulation is completed, the first gear is transferred to a quenching tank filled with polymer quenching liquid within 5-10 seconds; the circulation pump flow rate of the quenching tank filled with polymer quenching liquid is adjusted to 600-800L / min, and the flow rate of the polymer quenching liquid is adjusted so that the cooling rate of the first gear is 80-100°C / s; until the temperature of the first gear drops to 495-550°C, the first gear is transferred to a quenching tank filled with water-based coolant within 3-5 seconds; the circulation pump flow rate of the quenching tank filled with water-based coolant is adjusted to 300-500L / min, and the flow rate of the water-based coolant is adjusted so that the cooling rate of the first gear is 30-50°C / s, until the temperature of the first gear drops to 190-210°C, to obtain a second gear. Gradient quenching achieves different cooling rates for different parts of the gear, forming a hardened layer of a certain depth on the surface while maintaining good toughness within the gear. The formation of this hardened layer generates compressive stress on the surface, which effectively offsets some of the operating stress and improves the gear's load-bearing capacity. Furthermore, by controlling the quenching process parameters, excessive quenching stresses caused by excessively rapid cooling rates can be avoided, preventing gear deformation or cracking.

[0066] Carburizing and austempering the second gear to obtain a third gear;

[0067] Methods for obtaining third gear include:

[0068] The second gear is placed in a carburizing furnace and heated to 920-940°C at a rate of 10-15°C / min. The temperature is then maintained for carburizing for 4-6 hours. During the carburizing process, the carbon content in the furnace is reduced to 1.0%-1.2%. After the carburizing process is complete, the furnace is opened and, within 8-10 seconds, the second gear is transferred to an austempering furnace at 280-350°C for an isothermal salt bath, where it is maintained for 2 hours. After the isothermal bath, the second gear is removed and naturally cooled to room temperature, resulting in the third gear. Carburizing increases the carbon content on the gear surface. During the subsequent quenching and tempering processes, compressive stress is generated on the surface, improving the wear resistance and fatigue strength of the tooth surface. Isothermal tempering is maintained at a constant temperature for a period of time to fully transform the quenched microstructure, further eliminating quenching stresses, stabilizing the microstructure, and improving the dimensional stability of the gear.

[0069] Preset the scanning range, scanning step and scanning speed to collect X-ray diffraction patterns, neutron diffraction data and eddy current signals of the third gear surface; X-ray diffraction patterns can be obtained by high-precision XRD equipment, please refer to Figure 2Neutron diffraction data can be obtained by contacting a professional institution equipped with neutron diffraction experimental equipment, transporting the gear sample to the experimental site, and installing it in the neutron beam irradiation area according to standard procedures. Eddy current signals can be collected using high-resolution eddy current array testing equipment. These data reflect information such as the internal structure and residual stress of the gear. By analyzing X-ray diffraction patterns, neutron diffraction data, and eddy current signals, information such as the gear's grain size and lattice distortion can be obtained, thereby optimizing subsequent process parameters such as tempering, such as determining the most appropriate tempering temperature and time, to improve gear performance and quality.

[0070] Feature extraction is performed on X-ray diffraction patterns, neutron diffraction data, and eddy current signals to obtain X-ray diffraction features, neutron diffraction features, and eddy current features. These features are then combined to form a feature vector. This feature vector integrates information obtained from multiple testing methods, covering various aspects of the gear's structure, residual stress, and other characteristics. This vector, used as input, provides a rich data foundation for building an accurate parameter prediction model, enabling the model to more accurately predict process parameters such as tempering temperature and time, thereby optimizing the gear's heat treatment process and improving gear performance.

[0071] Methods for obtaining X-ray diffraction signatures include:

[0072] The position of each diffraction peak, the intensity value corresponding to the highest point of each diffraction peak, and the half-height width of each diffraction peak, that is, the width of the diffraction peak corresponding to half of the intensity value corresponding to the highest point of the diffraction peak, are extracted from the X-ray diffraction pattern; the position of the diffraction peak corresponds to the diffraction angle of Position, calculate the intensity ratio of adjacent diffraction peaks to obtain the peak intensity ratio; calculate the grain size of the third gear using the Scherrer formula ;in, is the Scherrer constant, generally taken as 0.89; is the wavelength of X-rays; is the width at half height; is the diffraction angle, that is, the angle between the incident X-ray and the crystal plane; calculate the residual stress corresponding to different azimuth angles ;in, is the elastic modulus; is Poisson's ratio; is the azimuth angle; the peak intensity ratio, grain size and residual stress are spliced together as the X-ray diffraction characteristics.

[0073] Methods for obtaining neutron diffraction signatures include:

[0074] Extract the diffraction peak displacement of the preset crystal plane at different depths from the neutron diffraction data and calculate the lattice strain ;in, is the diffraction peak shift; is the diffraction angle in the stress-free state; the internal stress is calculated according to Hooke's law ; Lattice strain and internal stress are spliced together as neutron diffraction features.

[0075] Methods for obtaining eddy current characteristics include:

[0076] Obtaining current from eddy current signals , and the current corresponding to the eddy current signal with changed phase and amplitude , calculate the crack depth ;in, and is the calibration coefficient, obtained by experimental fitting; calculate the crack size ;in, is the material resistivity; is the excitation frequency; is the vacuum permeability; is the relative magnetic permeability; the crack depth and crack size are combined to form the eddy current characteristic.

[0077] The eigenvector is used as input to the parameter prediction model to obtain the tempering temperature and tempering time. The third gear is then isothermally tempered based on the obtained tempering temperature and tempering time to obtain the fourth gear. Isothermal tempering based on the tempering temperature and time obtained by the parameter prediction model can more accurately eliminate residual stress within the gear and achieve a more stable structure. Precisely controlling the tempering process effectively adjusts the internal stress distribution of the gear, reducing residual stress to an appropriate level and improving the gear's fatigue life and dimensional stability. The parameter prediction model operates based on eigenvectors from multi-source data, changing the traditional empirical approach to setting tempering process parameters and enabling precise optimization of tempering process parameters. Tempering temperature and time determined based on the actual internal state of the gear can better meet gear performance requirements and improve the scientific nature and reliability of the heat treatment process.

[0078] The training methods for parameter prediction models include:

[0079] Q groups of training data are collected in advance. The training data include feature vectors, and tempering temperature and tempering time corresponding to the feature vectors.

[0080] The parameter prediction model is trained using training data, with the feature vector as the input of the parameter prediction model and the tempering temperature and tempering time as the output of the parameter prediction model. The stochastic gradient descent method is used to adjust the weights and biases of the parameter prediction model through the back propagation algorithm to minimize the error between the predicted results of the parameter prediction model and the actual results; a loss function is set, and the loss function is the mean square error; when the loss function value reaches convergence, the training of the parameter prediction model is stopped, and the parameter prediction model corresponding to the time when the loss function value reaches convergence is used as the trained parameter prediction model.

[0081] Methods for obtaining fourth gear include:

[0082] The third gear was placed in a heating furnace, and the temperature of the heating furnace was raised to the tempering temperature at a heating rate of 5-10°C / min, and then kept at the tempering temperature for the corresponding tempering time. The third gear was taken out of the heating furnace and naturally cooled to room temperature in air to obtain the fourth gear.

[0083] The fourth gear is strengthened through a multi-energy field coupling stress elimination process to obtain the fifth gear; the multi-energy field coupling stress elimination process eliminates magnetostrictive stress through pulsed electromagnetic field demagnetization, and the high-frequency ultrasonic impact and alternating annular magnetic field work together to induce dislocation slip and grain boundary migration, further eliminating residual stress, making the internal stress distribution of the gear more uniform, and greatly improving the fatigue strength and deformation resistance of the gear.

[0084] Reference Figure 3 , the method of obtaining the fifth gear includes:

[0085] Step 1: Demagnetize the fourth gear for 5 minutes using a pulsed electromagnetic field with a frequency of 1 kHz and a magnetic field strength of 1.5 T;

[0086] Step 2: Use high-frequency ultrasound with a frequency of 20 kHz and an amplitude of 80 μm to impact the root fillet of the fourth gear for 10 minutes, setting the impact energy density to 15 J / cm²; simultaneously apply an alternating toroidal magnetic field with a frequency of 50 Hz and a magnetic field strength of 0.8 T;

[0087] Step 3: Use Nd:YAG laser with a wavelength of 1064nm and an energy density of 10J / cm² to perform impact treatment on the fourth gear for 5 minutes to obtain the fifth gear.

[0088] The tooth profile data of the fifth gear was collected and then fine-machined using a deformation-compensating cutting strategy to produce a large rotary kiln gear. During the fine-machining process, the deformation-compensating cutting strategy reduces the additional stress generated by cutting forces by optimizing cutting parameters and adjusting tool paths. It also compensates for deformation that may have occurred during previous heat treatment and machining, avoiding stress concentration caused by deformation. This further improves the dimensional accuracy and surface quality of the gears, and ensures a more uniform stress distribution during operation. Based on the collected tooth profile data, cutting process parameters such as cutting speed, feed rate, cutting depth, and tool selection are adjusted in real time. The deformation-compensating strategy enables precise control of gear machining accuracy, ensuring that parameters such as the gear's tooth profile and tooth direction meet design requirements, improving the gear's transmission stability and load-bearing capacity, and optimizing the final stage of the entire gear manufacturing process.

[0089] Methods for obtaining large gears for rotary kilns include:

[0090] A laser scanning probe is used to measure the tooth profile of the fifth gear. The probe scans along the tooth profile of the fifth gear to obtain tooth profile data of the fifth gear. The tooth profile data of the fifth gear is compared with pre-designed tooth profile data, and tooth profile error data is calculated. The fifth gear is fine-machined according to the tooth profile error data based on the plasma-assisted cutting method. During the fine-machining process, the tooth profile of the fifth gear being machined is scanned and measured by the laser scanning probe at every preset time interval (e.g., 100ms). The measured tooth profile data of the fifth gear is compared with the pre-designed tooth profile data, and tooth profile error compensation data is calculated.

[0091] The method for fine-machining the fifth gear according to the tooth profile error data based on the plasma-assisted cutting method includes:

[0092] Ar and H2 are mixed in a ratio of 5:1-10:1 to obtain a mixed gas, and the mixed gas is introduced into a plasma generator. The plasma generator ionizes the mixed gas (such as by a high-frequency electric field or a radio-frequency electric field) to generate plasma, and the plasma generator is adjusted so that the temperature of the plasma is 110-130°C, and the plasma is injected into the cutting area at an injection pressure of 0.12 MPa; according to a preset cutting speed, a preset feed rate, a preset cutting depth, a preset rake angle, a preset clearance angle, and a preset cutting edge radius, the cutting tool is controlled to cut the fifth gear according to the tooth profile error data; for example, the preset cutting speed is 120 m / min, the preset feed rate is 0.15 mm / r, and the preset cutting depth is 0.5 mm, the rake angle of the cutting tool is controlled to be 10°, the clearance angle is 8°, and the cutting edge radius is 0.02 mm, and the fifth gear is cut according to the tooth profile error data.

[0093] Methods for obtaining tooth profile error compensation data include:

[0094] The heat treatment process parameters and the machining process parameters are used as inputs of the deformation compensation model to obtain tooth profile error data. The difference between the tooth profile error data and the actually measured tooth profile error data is calculated, and the difference is used as tooth profile error compensation data. The tooth profile of the fifth gear is compensated according to the tooth profile error compensation data. The heat treatment process parameters include the heating rate, furnace temperature, and holding time during the gear heat treatment process. The machining process parameters include the plasma mixing ratio, temperature, injection pressure, cutting speed, feed rate, cutting depth, and the rake angle, clearance angle, and edge radius of the cutting tool.

[0095] The training methods for the deformation compensation model include:

[0096] M groups of deformation compensation data are collected in advance, and the deformation compensation data include heat treatment process parameters, machining process parameters and tooth profile error data.

[0097] The heat treatment process parameters and machining process parameters are used as the input of the deformation compensation model, and the corresponding tooth profile error data is used as the output of the deformation compensation model. The weights and biases of the model are continuously adjusted through the back propagation algorithm to minimize the error between the predicted tooth profile error data and the actual tooth profile error data of the deformation compensation model. The mean square error is used as the loss function to train the deformation compensation model until the sum of the errors reaches convergence. The deformation compensation model corresponding to the time when the sum of the errors reaches convergence is regarded as the trained deformation compensation model.

[0098] Based on the preparation process of the above gears, large gears for rotary kiln were prepared. The performance of the first gear to the fifth gear during the preparation process was tested multiple times and the average value was obtained. The specific test data can be found in Table 1:

[0099] Table 1 Performance index data of different gears

[0100]

[0101] It can be seen from the above table:

[0102] For the first gear: The volume expansion of the nitrided layer on the first gear generates an initial compressive stress (-215.32 MPa), which can offset the potential tensile stress peaks (up to 350 MPa in the third gear) that may be generated during subsequent gradient quenching and carburizing, reducing the risk of overall stress imbalance. If nitriding is omitted, the tensile stress of the second gear after quenching could increase from 287.45 MPa to over 350 MPa, increasing the probability of cracking. Refining the grain size (17.50 μm) enhances the material's toughness base, ensuring a more uniform stress distribution during subsequent heat treatments (such as gradient quenching), avoiding stress concentration caused by coarse grains (with conventional processes, stress gradients can reach over 200 MPa with grains of 50-60 μm).

[0103] For the second gear: The surface martensite (hardness 59.20 HRC) provides wear resistance, while the core bainite (impact toughness 47.50J) retains impact resistance, achieving a balanced strength-toughness compared to traditional single-liquid quenching (all martensite, toughness ≤35J). Impact toughness is increased by 35.7%, enabling the gear to withstand the shock loads of rotary kiln startup (conventional processes are prone to tooth root fracture). Surface tensile stress (287.45MPa) is intentionally retained to allow for the subsequent compressive stress accumulation during carburization (tensile stress can be offset by approximately 30% after carburization), thus avoiding stress exceeding the limit in a single process (e.g., carburization directly generates 350MPa tensile stress on a zero-stress substrate, which is more risky).

[0104] Regarding the third gear: After carburizing, the surface carbon content reaches 1.1%, and the hardness after quenching reaches 61.85 HRC (compared to ≈59 HRC with conventional methods). This improves wear resistance by 20%, making it suitable for high-wear conditions (such as rotary kiln gear meshing). Austempering reduces the amount of retained austenite (from 30% to 15%), improving dimensional stability (deformation is 30% lower than with direct quenching). The martensitic transformation of the carburized layer generates a peak tensile stress of 350 MPa, far exceeding the material's fatigue strength threshold (≈250 MPa), necessitating dynamic tempering (conventional fixed tempering can only reduce it to above 150 MPa, still above the safety threshold). If the third gear is used directly, its fatigue life is 72.6% lower than that of the fifth gear, demonstrating the importance of tempering as a stress-saving measure.

[0105] For the fourth gear, dynamic tempering, through precise temperature (535.2°C, 14.8°C lower than the traditional 550°C) and time (2.3 hours, 15% longer), reduced tensile stress by 78.4%, shifting it to a dominant compressive stress (75.50 MPa), offsetting the tensile stress of the operating load (e.g., tensile stress on the tooth surface during meshing is ≈50 MPa). This compressive stress state extended fatigue crack initiation time from 500 hours (for the third gear) to 1200 hours (for the fifth gear), demonstrating that "stress type determines life." Tempered martensite replaces quenched martensite, increasing carbide dispersion (grains calculated by the Scherrer formula are 15.50 μm), boosting impact toughness from 43.20 J (for the third gear) to 76.30 J, resolving the "hard-brittle" contradiction inherent in traditional processes.

[0106] For the fifth gear: Ultrasonic impact treatment introduces a -300MPa peak compressive stress layer (depth 0.5mm) at the tooth root. Laser impact treatment superimposes deep compressive stress (1-2mm), bringing the surface comprehensive compressive stress to -82.75MPa. Traditional stress relief methods (such as shot peening and tempering) can only reach -30~-50MPa, significantly reducing the risk of tooth root bending fatigue. The fatigue life is reduced from 0.78×10 7 times increased to 2.85×10 7This directly proves that "stress optimization is the core driver of life extension." Stress equalization (gradient ≤ 50 MPa) after dynamic tempering provides a stable foundation for finishing. Combined with laser scanning compensation (such as fine-tuning the cutting depth by 0.005 mm), the tooth profile error is reduced from 0.065 mm (for the third gear) to 0.0125 mm, achieving ISO Class 1 accuracy and avoiding the cyclical errors of the traditional process: heat treatment deformation, tooth grinding correction, and secondary stress.

[0107] Example 2

[0108] See also Figure 4 As shown, the rotary kiln large gear heat treatment process optimization system described in this embodiment includes:

[0109] Material pretreatment module: performing normalizing forging twice on the preselected material to obtain a preselected material with refined grains, processing the preselected material with refined grains to obtain a gear, placing the gear in air for natural cooling, and performing vacuum nitriding treatment on the naturally cooled gear to obtain a first gear;

[0110] Heat treatment module: performing gradient quenching treatment on the first gear to obtain the second gear; performing carburizing treatment and isothermal quenching treatment on the second gear to obtain the third gear;

[0111] Detection optimization module: Preset the scanning range, scanning step size, and scanning speed to collect X-ray diffraction patterns, neutron diffraction data, and eddy current signals from the surface of the third gear; perform feature extraction on the X-ray diffraction patterns, neutron diffraction data, and eddy current signals to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; concatenate the X-ray diffraction features, neutron diffraction features, and eddy current features to obtain a feature vector; use the feature vector as input to a parameter prediction model to obtain a tempering temperature and tempering time, and perform isothermal tempering on the third gear based on the obtained tempering temperature and tempering time to obtain a fourth gear;

[0112] Post-processing module: Strengthen the fourth gear through a multi-energy field coupling stress relief process to obtain the fifth gear;

[0113] Finishing module: collects the tooth profile data of the fifth gear, and performs finish machining on the fifth gear through deformation compensation cutting strategy to obtain the large gear of the rotary kiln.

[0114] Reference Figure 5 The plasma mixture ratio of Ar to H₂ is 7:1, the plasma temperature is set at 120°C, and the injection pressure is 0.12 MPa. Real-time status monitoring shows that the plasma is currently operating normally, with a temperature of 125°C, a gas flow rate of 2.5 L / min, and a system pressure that is consistent with the injection pressure, 0.12 MPa. The system also indicates that the plasma parameters are within the optimal operating range.

[0115] The current cutting parameters are as follows: cutting speed 150 m / min, feed rate 0.2 mm / rev, cutting depth 2.5 mm, rake angle 15°, relief angle 8°, and cutting edge radius 0.8 mm. The system indicates that the current cutting depth is approaching the warning value and recommends appropriate adjustment.

[0116] The current tooth profile error is 0.015mm, and the compensation effect reaches 85%.

[0117] The temperature change trend chart shows that from 8 am to around 2 pm, the temperature is basically stable around 120℃, with small fluctuations, and the system is in a relatively stable state.

[0118] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

[0119] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A method for optimizing heat treatment process of large gears in a rotary kiln, characterized in that: The steps include: The preselected material is subjected to normalizing forging twice to obtain a preselected material with refined grains, the preselected material with refined grains is processed to obtain a gear, and the gear is subjected to vacuum nitriding treatment after natural cooling to obtain a first gear; performing a gradient quenching process on the first gear to obtain a second gear; Carburizing and austempering the second gear to obtain a third gear; Preset the scanning range, scanning step length and scanning speed to collect X-ray diffraction patterns, neutron diffraction data and eddy current signals from the surface of the third gear; Extract features from X-ray diffraction patterns, neutron diffraction data, and eddy current signals to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; and concatenate the X-ray diffraction features, neutron diffraction features, and eddy current features to obtain a feature vector. Methods for obtaining X-ray diffraction signatures include: The position of each diffraction peak, the intensity value corresponding to the highest point of each diffraction peak, and the half-height width of each diffraction peak, that is, the width of the diffraction peak corresponding to half of the intensity value corresponding to the highest point of the diffraction peak, are extracted from the X-ray diffraction pattern; the position of the diffraction peak corresponds to the diffraction angle of Position, calculate the intensity ratio of adjacent diffraction peaks to obtain the peak intensity ratio; calculate the grain size of the third gear using the Scherrer formula; calculate the residual stress corresponding to different azimuth angles; splice the peak intensity ratio, grain size and residual stress as the X-ray diffraction feature; Methods for obtaining neutron diffraction signatures include: Extract the diffraction peak shift of the preset crystal plane at different depths from the neutron diffraction data and calculate the lattice strain; calculate the internal stress according to Hooke's law; and combine the lattice strain and internal stress as the neutron diffraction feature; Methods for obtaining eddy current characteristics include: Obtain the current in the eddy current signal and the current corresponding to the eddy current signal with changed phase and amplitude, calculate the crack depth; calculate the crack size; and combine the crack depth and crack size as the eddy current feature; The characteristic vector is used as the input of the parameter prediction model to obtain the tempering temperature and tempering time, and the third gear is isothermally tempered according to the obtained tempering temperature and tempering time to obtain the fourth gear; Strengthening the fourth gear through a multi-energy field coupling stress relief process to obtain a fifth gear; The tooth profile data of the fifth gear is collected, and the fifth gear is fine-machined using a deformation compensation cutting strategy to obtain a large gear for a rotary kiln: the tooth profile of the fifth gear is measured using a laser scanning probe, the probe scans along the tooth profile of the fifth gear to obtain the tooth profile data of the fifth gear, the tooth profile data of the fifth gear is compared with the pre-designed tooth profile data, and the tooth profile error data is calculated. The fifth gear is fine-machined according to the tooth profile error data based on a plasma-assisted cutting method. During the fine-machining process, the tooth profile of the fifth gear being machined is scanned and measured once at preset time intervals using a laser scanning probe, the measured tooth profile data of the fifth gear is compared with the pre-designed tooth profile data, and the tooth profile error compensation data is calculated.

2. The method for optimizing heat treatment process of large gears of rotary kiln according to claim 1, characterized in that: Methods for obtaining third gear include: The second gear is placed in a carburizing furnace, heated to 920-940°C at a rate of 10-15°C / min, and then carburized for 4-6 hours. During the carburizing process, the carbon content in the carburizing furnace is 1.0%-1.2%. After the carburizing is completed, the carburizing furnace is opened and the second gear is transferred to an isothermal quenching furnace at 280-350°C within 8-10 seconds for an isothermal salt bath, and kept warm for 2 hours. After the insulation is completed, the second gear is taken out and naturally cooled to room temperature to obtain the third gear.

3. The method for optimizing heat treatment process of large gears of rotary kiln according to claim 1, characterized in that: Methods for obtaining fourth gear include: The third gear was placed in a heating furnace, and the temperature of the heating furnace was raised to the tempering temperature at a heating rate of 5-10°C / min, and then kept at the tempering temperature for the corresponding tempering time. The third gear was taken out of the heating furnace and naturally cooled to room temperature in air to obtain the fourth gear.

4. The method for optimizing heat treatment process of large gears of rotary kiln according to claim 1, characterized in that: Methods for obtaining the second gear include: The first gear is placed in a quenching furnace, the temperature of the quenching furnace is raised to 860°C at a rate of 10-15°C / min, and then kept warm for 1.5-2 hours. After the insulation is completed, the first gear is transferred to a quenching tank filled with polymer quenching liquid within 5-10 seconds; the circulation pump flow rate of the quenching tank filled with polymer quenching liquid is adjusted to 600-800L / min, and the flow rate of the polymer quenching liquid is adjusted so that the cooling rate of the first gear is 80-100°C / s; until the temperature of the first gear drops to 495-550°C, the first gear is transferred to a quenching tank filled with water-based coolant within 3-5 seconds; the circulation pump flow rate of the quenching tank filled with water-based coolant is adjusted to 300-500L / min, and the flow rate of the water-based coolant is adjusted so that the cooling rate of the first gear is 30-50°C / s, until the temperature of the first gear drops to 190-210°C, to obtain a second gear.

5. The method for optimizing heat treatment process of large gears of rotary kiln according to claim 1, characterized in that: Methods for obtaining fifth gear include: Step 1: Demagnetize the fourth gear for 5 minutes using a pulsed electromagnetic field with a frequency of 1 kHz and a magnetic field strength of 1.5 T; Step 2: Use high-frequency ultrasound with a frequency of 20 kHz and an amplitude of 80 μm to impact the root fillet of the fourth gear for 10 minutes, setting the impact energy density to 15 J / cm²; simultaneously apply an alternating toroidal magnetic field with a frequency of 50 Hz and a magnetic field strength of 0.8 T; Step 3: Use Nd:YAG laser with a wavelength of 1064nm and an energy density of 10J / cm² to perform impact treatment on the fourth gear for 5 minutes to obtain the fifth gear.

6. The method for optimizing heat treatment process of large gears of rotary kiln according to claim 1, characterized in that: The method for fine-machining the fifth gear according to the tooth profile error data based on the plasma-assisted cutting method includes: Ar and H2 are mixed in a ratio of 5:1-10:1 to obtain a mixed gas, the mixed gas is introduced into a plasma generator, the plasma generator ionizes the mixed gas to generate plasma, the plasma generator is adjusted so that the temperature of the plasma is 110-130° C., and the plasma is injected into the cutting area at an injection pressure of 0.12 MPa; and a cutting tool is controlled to cut the fifth gear according to a preset cutting speed, a preset feed rate, a preset cutting depth, a preset rake angle, a preset clearance angle, and a preset edge radius to perform cutting processing according to the tooth profile error data; Methods for obtaining tooth profile error compensation data include: The heat treatment process parameters and machining process parameters are used as inputs of the deformation compensation model to obtain tooth profile error data. The difference between the tooth profile error data and the actually measured tooth profile error data is calculated, and the difference is used as the tooth profile error compensation data. The tooth profile of the fifth gear is compensated according to the tooth profile error compensation data. The heat treatment process parameters include the heating rate, furnace temperature and holding time during the gear heat treatment process. The machining process parameters include the plasma mixing ratio, temperature, injection pressure, cutting speed, feed rate, cutting depth, as well as the rake angle, clearance angle and edge radius of the cutting tool.

7. The method for optimizing heat treatment process of large gears of rotary kiln according to claim 1, characterized in that: Methods for obtaining preselected materials with refined grains include: The preselected material is placed in a heating furnace, the temperature of the heating furnace is increased to 890°C at a heating rate of 5-10°C / min, and then kept warm for 4 hours. The preselected material is taken out of the heating furnace and naturally cooled to room temperature in the air; the preselected material is placed in a heating furnace again, the temperature of the heating furnace is increased to 850°C at a heating rate of 5-10°C / min, and then kept warm for 3 hours. The preselected material is taken out of the heating furnace and naturally cooled to room temperature in the air to obtain a preselected material with refined grains.

8. The method for optimizing heat treatment process of large gears of rotary kiln according to claim 1, characterized in that: Methods for obtaining the first gear include: After natural cooling, the gear is placed in a vacuum furnace with a pressure of 10-100Pa, and nitrogen is introduced into the vacuum furnace until the pressure inside the vacuum furnace is 500-1000Pa. The temperature of the heating furnace is raised to 520℃ at a heating rate of 5-10℃ / min and then kept warm for 8h. After the insulation is completed, wait for the temperature of the heating furnace to drop to room temperature, turn off the nitrogen, and take out the gear in the heating furnace to obtain the first gear.

9. A rotary kiln large gear heat treatment process optimization system, which implements the rotary kiln large gear heat treatment process optimization method according to any one of claims 1 to 8, characterized in that: include: Material pretreatment module: performing normalizing forging twice on the preselected material to obtain a preselected material with refined grains, processing the preselected material with refined grains to obtain a gear, placing the gear in air for natural cooling, and performing vacuum nitriding treatment on the naturally cooled gear to obtain a first gear; Heat treatment module: performing gradient quenching treatment on the first gear to obtain the second gear; Carburizing and austempering the second gear to obtain a third gear; Detection optimization module: Preset the scanning range, scanning step size, and scanning speed to collect X-ray diffraction patterns, neutron diffraction data, and eddy current signals from the surface of the third gear; perform feature extraction on the X-ray diffraction patterns, neutron diffraction data, and eddy current signals to obtain X-ray diffraction features, neutron diffraction features, and eddy current features; and concatenate the X-ray diffraction features, neutron diffraction features, and eddy current features to obtain a feature vector. The characteristic vector is used as the input of the parameter prediction model to obtain the tempering temperature and tempering time, and the third gear is isothermally tempered according to the obtained tempering temperature and tempering time to obtain the fourth gear; Post-processing module: Strengthen the fourth gear through a multi-energy field coupling stress relief process to obtain the fifth gear; Finishing module: collects the tooth profile data of the fifth gear, and performs finish machining on the fifth gear through deformation compensation cutting strategy to obtain the large gear of the rotary kiln.

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